34 research outputs found
Photon echo without a free induction decay in a double-Lambda system
We have characterized a novel photon-echo pulse sequence for a
double- type energy level system where the input and rephasing
transitions are different to the applied -pulses. We show that despite
having imperfect -pulses (associated with large coherent emission due to
free induction decay), the noise added is only 0.0190.001 relative to the
shot noise in the spectral mode of the echo. Using this echo pulse sequence in
the `rephased amplified spontaneous emission' (RASE) scheme
\cite{Ledingham2010} will allow for generation of entangled photon pairs that
are in different frequency, temporal, and potentially spatial modes to any
bright driving fields. The coherence and efficiency properties of this sequence
were characterized in a Pr:YSO crystal
Long spin coherence times in the ground state and an optically excited state of Er:YSiO at zero magnetic field
Spins in solids are an ideal candidate to act as a memory and interface with
superconducting qubits due to their long coherence times. We spectroscopically
investigate erbium-167-doped yttrium orthosilicate as a possible
microwave-addressed memory employing its microwave frequency transitions that
occur without applying an external magnetic field. We obtain coherence times of
380 s in a ground state spin transition and 1.48 ms in an excited state
spin transition. This is 28 times longer compared to previous zero field
measurements, as well as 200 times longer than a previous microwave memory
demonstration in the same material. These long coherence times show that
erbium-167-doped yttrium orthosilicate has potential as a microwave-addressed
quantum memory.Comment: 9 pages, 7 figures. The paper has been expanded compared to the
previous version on arXiv, and the title has change
Non-classical photon streams using rephased amplified spontaneous emission
We present a fully quantum mechanical treatment of optically rephased photon
echoes. These echoes exhibit noise due to amplified spontaneous emission,
however this noise can be seen as a consequence of the entanglement between the
atoms and the output light. With a rephasing pulse one can get an "echo" of the
amplified spontaneous emission, leading to light with nonclassical correlations
at points separated in time, which is of interest in the context of building
wide bandwidth quantum repeaters. We also suggest a wideband version of DLCZ
protocol based on the same ideas.Comment: 5 pages, 4 figures. Added section